Thermoforming is a process for creating various products by heating thermoformable material and causing the heated material to form onto at least a portion of an object and create an impression of at least a portion of the object in the thermoformable material. The thermoformable material may be a sheet which is placed in a thermoforming machine which when operated, heats the thermoformable sheet and causes the heated thermoformable sheet to form onto at least a portion of the object and create an impression of at least a portion of the object in the heated thermoformable sheet. A vacuum may be used to draw the heated sheet into intimate contact with the object. The impression created in the sheet is retained when the sheet cools.
Thermoforming machines are commonly used in dentists' offices and dental laboratories for creating thermoformed impressions of objects used in the practice of dentistry which includes not only general dentistry but also dental specialties such as orthodontia for example. Applicant's U.S. Pat. No. 9,526,591, issued Dec. 27, 2016, discloses a method of thermoforming a thin sheet of thermoformable material onto a dental arch model.
A typical practice for using a thermoforming machine involves manually placing a perimeter margin of a thin sheet of thermoformable material on an open-center platen of the machine and closing an open-center cover onto the perimeter margin of the sheet to hold the sheet in proper position for thermoforming onto an object such as a dental arch model. The thermoforming machine comprises a base on which the object is placed. With a sheet of thermoformable material held between the platen and the cover, the sheet is heated and begins to droop. With the platen and the closed cover holding the perimeter margin of the sheet, they are moved downward to drape the drooping sheet over the object while cooperating with the base to form a closed space within which the object is disposed with the sheet draped over it. Vacuum is then drawn within the closed space through multiple passages in the base to cause the draped sheet to more intimately form onto the object. After that, the vacuum is turned off and the sheet is allowed to cool. Upon completion of cooling, the formed sheet is removed from the object, retaining an impression of the object.
When the object is a model of a dental arch, or portion of such a model, an impression of teeth of the model, and any devices which may be affixed to the model, are captured in fixed form in the thermoformed material. As described in the above-mentioned patent, devices such as orthodontic brackets which are releasably mounted on the model may be captured in the thermoformed material and separate from the model along with the thermoformed material during removal of the material from the model.
Thinness of a sheet of thermoformable material may be an important factor in the quality of a resulting impression because it can affect the ability of the thermoformable material to form around an object with a desired degree of precision. In general, a very thin sheet can be formed around an object with greater precision than can a thicker sheet.